Oil and gas drilling processes have been developed wherein the bore hole initially is vertical and then turns to a horizontal orientation. Utilizing prior art techniques, for example, a down-hole of about 5,000 foot depth may be formed and then a horizontal hole can be formed starting at a down-hole location that can extend, depending upon various subterranean factors, from 500 to 800 feet horizontally. One problem with prior art drill strings is frictional drag. Another problem is helical stack-out. Helical stack-out is defined as the tendency of the drill string to distort into a helical configuration within the horizontal section of the bore hole causing a loss of drill weight, or pressure, after the horizontal bore hole extends 500 or so feet.
Connectors between drill strings are generally simple structures allowing for threaded connection to adjacent sections of drill pipe or tubing.
Centralizers, such as that shown in U.S. Pat. No. 5,358,042, issued to Stoltz, have been developed for use in cased holes. The centralizers disclosed in this patent include spherical roller elements mounted on centralizer support arms that extend radially outward of the drill string. Rollers extend radially outward to a point at which the rollers engage the inner surface of the casing. This apparatus is intended for finalizing installation of equipment in a bore hole and not for a primary drilling operation.
Also known in the industry are down-hole stabilizers such as that disclosed in U.S. Pat. No. 4,958,692, issued to Anderson. The stabilizer disclosed in the Anderson patent is a reamer which is intended to be mounted adjacent the drill bit. The stabilizer includes a plurality of rolling bearings individually mounted in pockets on the periphery of the stabilizer. The stabilizer also includes helically disposed fins or blades that function as a cutter in addition to functioning as a reamer. Only one such device is intended to be used in a drill string and it does not solve the problem of helical stack-out or minimize frictional drag along the length of the drill string. Due to the high cost of reamers, it is unfeasible to use a series of reamers between lengths of a drill string.
A substantial increase in oil production can be achieved if the length of horizontal drilling is extended to reach additional deposits of oil from a down-hole bore. Such a result is not possible with prior art drilling equipment.
Another problem is the need to remove drill cuttings from the bore hole. Fluid is pumped down through the drill string to the drill bit. Drill cuttings are removed by the backflow of drilling fluid between the outer wall of the drill string and the inner diameter of the bore hole. Pump sweeps are performed wherein a thickened suspension is pumped through the bore hole to suspend cuttings in a mud-like gel. While a certain amount of turbulence is present adjacent the drill bit, no prior art system is known that creates fluid turbulence at spaced intervals along the drill string for the purpose of enhancing removal of cuttings.
Prior art drilling equipment and techniques, when used in a horizontal bore hole, fail to provide the simple and effective solution summarized below.
For the foregoing reasons, there is a need for a drill string connector and system for inhibiting helical stack-out that overcomes the problems and limitations of the prior art.